The Linux FPGA

It was never unusual to have a CPU and an FPGA together. After all, each has different strengths and weaknesses. However, newer devices like the Xilinx Zynq have both a CPU and an FPGA in the same package. That means your design has to span hardware, FPGA configurations, and software. [Mitchell Orsucci] was using a Zynq device on a ArtyZ7-20 board and decided he wanted to use Linux to operate the ARM processor and provide user-space tools to interface with the FPGA and reconfigure it dynamically.

This sounds like a big project and it certainly isn’t trivial by any means. However, the Xilinx tools do a lot of the heavy lifting, including setting up the Linux kernel and a suitable root file system. The bulk of [Mitchell’s] work was in developing user space tools for Linux programs to interact with the FPGA hardware. You can see a short video demo below.

Continue reading “The Linux FPGA”

Linux Fu: X Command

Text-based Linux and Unix systems are easy to manipulate. The way the Unix I/O system works you can always fake keyboard input to another program and intercept its output. The whole system is made to work that way. Graphical X11 programs are another matter, though. Is there a way to control X11 programs like you control text programs? The answer to that question depends on exactly what you want to do, but the general answer is yes.

As usual for Linux and Unix, though, there are many ways to get to that answer. If you really want fine-grained control over programs, some programs offer control via a special mechanism known as D-Bus. This allows programs to expose data and methods that other programs can use. In a perfect world your target program will use D-Bus but that is now always the case. So today we’ll look more for control of arbitrary programs.

There are several programs that can control X windows in some way or another. There’s a tool called xdo that you don’t hear much about. More common is xdotool and I’ll show you an example of that. Also, wmctrl can perform some similar functions. There’s also autokey which is a subset of the popular Windows program AutoHotKey.

Continue reading “Linux Fu: X Command”

Linux Graphics Programming

There was a time when embedded system developers didn’t need to worry about graphics. When you have a PIC processor and two-line LCD, there isn’t much to learn. But if you are deploying Linux-based systems today, graphics are a real possibility. There are many options for doing Linux graphics including Wayland, X11, and frame buffers. Confused? This tutorial can help. The sections on Wayland and Mir are under construction, but that’s probably not what you are going to be using on a typical hacker project for the foreseeable future, anyway.

Of course, even inside those broad categories, you have multiple choices. If you are doing X11, for example, you can go low-level or pick any of a number of high-level libraries.

Continue reading “Linux Graphics Programming”

Linux Fu: Better Bash Scripting

It is easy to dismiss bash — the typical Linux shell program — as just a command prompt that allows scripting. Bash, however, is a full-blown programming language. I wouldn’t presume to tell you that it is as fast as a compiled C program, but that’s not why it exists. While a lot of people use shell scripts as an analog to a batch file in MSDOS, it can do so much more than that. Contrary to what you might think after a casual glance, it is entirely possible to write scripts that are reliable and robust enough to use in many embedded systems on a Raspberry Pi or similar computer.

I say that because sometimes bash gets a bad reputation. For one thing, it emphasizes ease-of-use. So while it has features that can promote making a robust script, you have to know to turn those features on. Another issue is that a lot of the functionality you’ll use in writing a bash script doesn’t come from bash, it comes from Linux commands (or whatever environment you are using; I’m going to assume some Linux distribution). If those programs do bad things, that isn’t a problem specific to bash.

One other limiting issue to bash is that many people (and I’m one of them) tend to write scripts using constructs that are compatible with older shells. Often times bash can do things better or neater, but we still use the older ways. For example:

Continue reading “Linux Fu: Better Bash Scripting”

Linux-Fu: Running Commands

One of the things that makes Linux and Unix-like systems both powerful and frustrating is that there are many ways to accomplish any particular goal. Take something simple like running a bunch of commands in sequence as an example. The obvious way is to write a shell script which offers a tremendous amount of flexibility. But what if you just want some set of commands to run? It sounds simple, but there are a lot of ways to issue a sequence of commands ranging from just typing them in, to scheduling them, to monitoring them the way a mainframe computer might monitor batch jobs.

Let’s jump in and take a look at a few ways you can execute sequences from bash (and many other Linux shells). This is cover the cron and at commands along with a batch processing system called task spooler. Like most things in Linux, this isn’t even close to a complete list, but it should give you some ideas on ways to control sequences of execution.

Continue reading “Linux-Fu: Running Commands”

Free as in Beer, or the Story of Windows Viruses

Whenever there’s a new Windows virus out there wreaking global havoc, the Linux types get smug. “That’ll never happen in our open operating system,” they say. “There are many eyes looking over the source code.” But then there’s a Heartbleed vulnerability that keeps them humble for a little while. Anyway, at least patches are propagated faster in the Linux world, right?

While the Linuxers are holier-than-thou, the Windows folks get defensive. They say that the problem isn’t with Windows, it’s just that it’s the number one target because it’s the most popular OS. Wrong, that’d be Android for the last few years, or Linux since forever in the server space. Then they say it’s a failure to apply patches and upgrade their systems, because their users are just less savvy, but that some new update system will solve the problem.

There’s some truth to the viruses and the patching, but when WannaCry is taking over hospitals’ IT systems or the radiation monitoring network at Chernobyl, it’s not likely to be the fault of the stereotypical naive users, and any automatic patch system is only likely to help around the margins.

So why is WannaCry, and variants, hitting unpatched XP machines, managed by professionals, all over the world? Why are there still XP machines in professional environments anyway? And what does any of this have to do with free software? The answer to all of these questions can be found in the ancient root of all evil, the want of money. Linux is more secure, ironically, at least partly because it’s free as in beer, and upgrading to a newer version is simply cheaper.

Continue reading “Free as in Beer, or the Story of Windows Viruses”

EV3DEV Lego Linux Updated

The ev3dev Linux distribution got an update this month. The distribution targets the Lego EV3 which is a CPU Lego provides to drive their Mindstorm robots. The new release includes the most recent kernel and updates from Debian 8.8. It also contains tools needed for some Wi-Fi dongles and other updates.

If you haven’t seen ev3dev before, it is quite simply Linux that boots on the EV3 hardware using an SD card. You don’t have to reflash the computer and if you want to return to stock, just take out the SD card. You can also use ev3dev on a Raspberry Pi or BeagleBone, if you like. There’s a driver framework included for handling sensors, motors, and other items using the file system.

Continue reading “EV3DEV Lego Linux Updated”